A study on tapping wrought aluminum (1st Report)

Abstract

The tapping (tapping for screwing) test for wrought aluminum alloys is reported in th paper. Three sorts of alloys, or 17S and 24S as typical alloys of high tensile strength and 56S as an anticorrosion alloy, were examined for tapping machinability such as tapping resistance, state of rough surface, accuracy of finished surface, etc.The results obtained were summarized as follows.The tapping torque was not affected by cutting speed of 5-10m/min in this experiment, but the torque at a constant rake angle slightly increased with the increase in tapping load. The torques varied according to the sorts of materials. Their values were arranged in ascending order of 24 S-F, 17 S-F, and 56 S-F, among which 24 S-F gave the most stable value, while the latter two gave unstable ones, having large deviation. It seemed that the state of finished surface was dependent upon rake angle and tapping load, but was independent of cutting speed; and there would be found out optimum tapping conditions for obtaining the best surface state. It was observed that the pitch of thread agreed with the tap within the limit of ever in measurement regardless of tapping conditions, and the angle of thread was larger by 30-60' than that of tap. The value of microhardness tended to increase up to about Hv=10-20 in the neighborgood of tapped surface.